Collimators are frequently used in radiation imagers to ensure that only radiation beams passing along a direct path from the known radiation source strike the detector thereby minimizing detection of beams of scattered or secondary radiation. Particularly in radiation imagers used for medical diagnostic analysis or for non-destructive evaluation procedures, it is important that only radiation emanating from a known source and passing along a direct path from that source be detected and processed by the imaging equipment. If the detector is struck by undesired radiation such as that passing along non-direct paths to the detector, performance of the imaging system can be compromised.
One diagnostic technology that incorporates collimators is the gamma camera typically utilized in Single Photon Emission Computed Tomography (SPECT) scanning, which is a nuclear medicine procedure in which gamma camera(s) have traditionally rotated around the patient taking pictures from many angles. From these images, a computer is employed to form a tomographic (cross-sectional) image of the internal area-of-interest within the patient using a calculation process that is similar to that used in X-ray Computed Tomography (CT) and in Positron Emission computed Tomography (PET).
In the instance of SPECT scanning, a subject (patient) is infused with a radioactive substance that emits gamma rays. Conventionally, a gamma camera includes a transducer to receive the gamma rays and record an image therefrom. In order for the image to be a true representation of the subject being studied, a collimator having collimating apertures (referred to as channels) is positioned between the transducer and the subject to screen out all of the gamma rays except those directed along a straight line through the collimator channels between a particular part of the subject and a corresponding particular part of the transducer. Traditionally, the collimator is made of a radiation opaque material such as lead, and collimating channels have been formed therein by various means such as drilling, casting, or lamination of corrugated strips of lead foil.
Owing to limitations in current manufacturing techniques, collimating channels have angular pointing errors. These errors cause distortions in the resulting nuclear medicine images, particularly those of Single Photon Emission Computed Tomography (SPECT) systems. Thus, it would be desirable to have a system and method that can provide correction for such angular pointing errors in the collimator channels in order to reduce image distortions and improve nuclear medicine image resolution.